Dimmers typically include a dimmer circuit and a user interface (e.g. a rotary knob) to control power, in particular alternating current (AC) mains power, to a load, such as a light source. In one existing example of a dimmer, a light source can be dimmed using a phase controlled dimmer, whereby power provided to the load is controlled by varying the amount of time that a switch connecting the load to a mains power source is conducting during a cycle of the AC (e.g. varying the duty cycle). Specifically, in this example, AC power to the load is switched ON and OFF during each half cycle of alternating current and the amount of dimming of the load is provided by the amount of ON time in relation to the OFF time for each half cycle.
Phase control dimmer circuits generally operate as trailing edge or leading edge dimmer circuits, and the two circuits are suited to different applications. In leading edge circuits, power is switched OFF at the beginning of each half cycle. In trailing edge circuits, power is switched OFF later in each half cycle (e.g. towards the end of each half cycle). Leading edge dimmer circuits are generally better suited to controlling power to inductive loads, such as small fan motors and iron core low voltage lighting transformers. Trailing edge dimmer circuits, on the other hand, are generally better suited to controlling power to capacitive loads, such as drivers for Light Emitting Diode (LED) lights.
In some applications, a dimmer system including more than one user interface for a dimmer is employed to control a load. For example, in a room with multiple entry ways, multiple user interfaces at each of the entry ways communicate with a central dimmer to control the load which is say an LED light source for the room. Existing examples of dimmer systems with multiple inputs include variations of a dimmer system with a central master dimmer controlling the light source and multiple slave dimmer inputs. More specifically, the central master dimmer is a phase control dimmer and the multiple slave dimmer inputs simply remotely control the central dimmer via some type of communication means. In these existing examples, however, the central dimmer requires an additional input for the additional signalling between the slave dimmer inputs and the master dimmer. The additional input may be, for instance, a radio frequency (RF) input for transmitting/receiving RF dimmer control signals or an extra low voltage wire input for transmitting/receiving dimmer control signals over an extra low voltage bus control system.